The present invention relates to an adjustable hinge for a motor-vehicle seat. More particularly this invention concerns a hinge which can tilt the back part of a motor-vehicle seat in stepless fashion relative to the seat part thereof.
An adjustable hinge for a motor-vehicle seat is known from U.S. Pat. No. 3,401,979 and German patent publication 1,580,543 which has a pair of hinge elements relatively steplessly displaceable so that the angle of the back part of the seat can be varied relative to the seat part. To this end one of the hinge elements is connected to one of these parts and the other element is connected to the other part. The one element has an inwardly directed array of inner teeth centered on a respective axis and the other part has an outwardly directed array of outer teeth centered on another axis spaced from the first-mentioned axis. The array of outer teeth has less teeth than the array of inner teeth, typically one less tooth, and is of smaller diameter so that the outer teeth can fit within the inner teeth with only a few of the teeth engaged.
In such an arrangement means is provided for orbiting one of the axes about the other axis and thereby rolling the inner teeth around inside the outer teeth, and correspondingly displacing the entire back part relative to the axis of the array of the seat part. As the inner teeth roll off inside the outer teeth the angle formed between the back part and seat part is changed.
Such an arrangement has the advantage that it allows stepless adjustment of the back part relative to the seat part. Furthermore the distribution of forces within the adjustable hinge is such that the setting does not change due to vibration or forces exerted on the back part.
Such adjustable hinges are typically, however, relatively bulky and expensive to manufacture. In particular the standard practice is to bolt the array of inner teeth in the form of a pinion on the fixed element connected to the seat part of the seat and to bolt the outer array in the form of a ring gear on the movable element connected to the back part. A collar is mounted on the pinion and centered on the respective axis thereof and a sleeve arrangement is mounted on the ring gear and in turn centered on its axis. An eccentric ring is fitted between the collar and the sleeve and is normally constituted of synthetic-resin material. Thus the element is axially relatively long and is formed of a large number of parts so that its assembly is relatively difficult and expensive.